In relation to a radio communication system for mobile communication, such as a portable phone, it has been contemplated to improve a transmission rate by means of various multiplexing techniques. In connection with a recent radio communication system for use with mobile communication, a frequency multiplexing scheme, such as an OFDM (Orthogonal Frequency Division Multiplexing), that is used also in; for instance, a wireless LAN and a digital terrestrial broadcasting, has been under consideration. Adopting the frequency multiplexing scheme makes it possible to prevent deterioration of transmission quality, which would otherwise be caused by fading, or the like, and to speed up and enhance quality of radio transmission. In order to improve fading resistance, frequency hopping (FH) is sometimes adopted into the frequency multiplexing scheme, such as an OFDM. The frequency hopping is a technique of hourly changing a frequency band to be used among a plurality of frequency bands, thereby preventing use of only a specific frequency band and preventing deterioration of performance, which would otherwise be caused by frequency selective fading.
For instance, Patent Document 1 shows a proposal of a method for reducing interference with another device utilizing the same radio communication system by shifting a frequency hopping period of a retransmission packet in a radio communication system, such as Bluetooth (Registered Trademark), that performs repetition in a time domain (also called a “Time spreading scheme”) and frequency hopping.
FIG. 19 shows example operation of the related art described in connection with Patent Document 1. FIG. 19(a) shows a frequency hopping pattern at the time of first transmission. An upper chart shows a desired signal, and a lower chart shows an interference signal (a signal which is intended for another device and which will interfere with a concerned device). In the example, the number of repetitions (Repetition Factor: RPF) to be performed in a time domain is set to two. In FIG. 19(a), when attention is paid to; for instance, a packet (1), a first packet located in a frequency band f1 and a second packet located in f2 are understood to be arranged as desired signals in the same time and frequency band as that of the interference signal. The same also applies to a packet (4). In such a state, a desired signal suffers great interference by the interference signal, so that a receiving side encounters difficulty in demodulating the desired signal.
For this reason, in the related art described in connection with Patent Document 1, a period of frequency hopping is shifted for a retransmission packet as shown in: FIG. 19(b). When interference appearing in FIG. 19(b) is observed, a first packet of a packet (1) of the desired signal, a second packet of a packet (3) of the same signal, a first packet of a packet (4) of the same signal, and a second packet of a packet (6) of the same signal suffer interference by the interference signal. However, in each of the packets, not both of the packets resultant from repetition suffered from interference. Therefore, it becomes possible to generate received data by demodulating the packet not subjected to interference.
Adoption of frequency hopping has been under consideration even in connection with an uplink channel of a 3GPP Long Term Evolution (hereinafter abbreviated as an “LTE”) network that is the next generation mobile communication standards. When a frame format for an uplink channel of the LTE network is viewed in a direction of a time axis, one slot includes seven transmission symbols, and two slots make up one subframe. Further, only one reference signal that is to serve as a pilot signal is arranged at the center of each slot (including seven symbols).
Adopting frequency hopping effected on a per-slot basis or a per-subframe basis as frequency hopping has been under consideration in connection with such an uplink channel of the LTE network. It has generally been said that a frequency interleave effect is yielded by adoption of frequency hopping, to thus improve a throughput.    Patent Document 1: JP-A-2006-333358